Polysilazanes are Si—N—Si linkage-bearing compounds having very high reactivity. By virtue of their reactivity, they are often used as surface treating agents. Owing to high reactivity, they are difficult to handle and tend to gel or build up their molecular weight during synthesis.
Perfluoropolyether-modified polysilazanes are generally produced by converting a perfluoropolyether having functionality at one end into silazane. This is because gelation can often occur during the reaction if a perfluoropolyether having functionality at both ends is used. While perfluoropolyethers having [(CF2O)p(CF2CF2O)q] in their backbone structure are believed effective for wiping off smears, only dual end functional perfluoropolyethers are commercially available.
Patent Document 1 discloses perfluoropolyether-modified polysilazanes having the formula (A):F(CxF2xO)mCyF2y-Q-Si(NH)1.5  (A)wherein Q is a divalent organic group, m is an integer of at least 1, x and y each are an integer of 1 to 3. They exhibit excellent water repellency, oil repellency and alkaline durability. However, those perfluoropolyether-modified polysilazanes used in Examples of Patent Document 1 are still unsatisfactory in surface slip and smear wipe-off.
In the industry, there is a demand for a surface treating agent having better properties including water/oil repellency, surface slip and smear wipe-off.